It is generally considered desirable to reduce noises generated from appliances, and from within buildings, vehicles, and the like. With respect to vehicles, road noise, tire noise, engine noise, vehicle vibrations, etc., may pass through a vehicle body and into the passenger compartment.
It is generally considered desirable to reduce the level of noise within a vehicle passenger compartment. Noises, such as road noise, engine noise, vibrations, etc., may be attenuated through the use of various acoustically absorptive (or reflective) materials. For example, sound attenuating materials are conventionally provided in conjunction with carpeting, door panels, and headliners.
Various sound attenuating materials have been developed for use in reducing noise levels within passenger compartments of vehicles. For example, U.S. Pat. No. 4,851,283 to Holtrop et al., proposes a thermoformable laminate for use in headliners. The headliner comprises a non-woven fabric bonded to a foamed polymer sheet. The fabric is formed from a blend of low melting staple fibers and high melting staple fibers.
U.S. Pat. No. 5,298,694 to Thompson proposes a non-woven acoustical insulation web. The web comprises thermoplastic fibers, and particularly a blend of melt-blown microfibers and crimped bulking fibers.
U.S. Pat. No. 5,677,027 to Masuda et al., proposes a sound insulating structure comprising a covering layer, a panel, and a cushioning layer. The cushioning layer comprises a first fiber such as polyethylene terephthalate (PET) and a second fiber that is of a shell-core construction wherein the majority of the core is PET.
U.S. Pat. No. 5,817,408 to Orimo et al., proposes a sound insulating structure which includes low and high density thermoplastic fibers. PET is preferred as a thermoplastic synthetic fiber.
U.S. Pat. No. 4,529,639 to Peoples, Jr. et al. proposes a molded foam-backed carpet assembly which includes a carpet layer, a moldable thermoplastic polymer layer and one or more foam pads fusibly bonded to the thermoplastic layer and extending over less than the entire surface of the thermoplastic polymer layer to provide desired cushioning and sound and thermal insulation only in preselected areas of the carpet.
In general, the ability of conventional materials to attenuate sound increases as the amount of material increases. Unfortunately, increased materials often increases the weight of sound attenuating material, which may be undesirable. Accordingly, there is a continuing need for acoustical insulation materials that exhibit superior sound attenuating properties, while also being lightweight and low in cost.